1. Field of the Invention
The present invention relates to a process for the preparation of electrically conductive polymers based on polythiophenes (also called doped polythiophenes) by chemical polymerization of thiophene.
2. Description of the Related Art
A process for preparing aromatic polymers by chemical polymerization in the presence of a Friedel-Crafts catalyst, such as ferric chloride, at a temperature of between 100.degree. and 800.degree. C., was proposed in Patent DE 1,178,529. The polymers obtained by this process have conductivities of between 10.sup.-10 and 10.sup.-0.5 siemens per cm.
The polymerization of thiophene is usually carried out by an electrochemical route in order to obtain products which are reasonably reproducible.
However, these electrochemical polymerization processes result in polymers which are poorly conductive, thermally unstable and difficult to process. Furthermore, in most cases the degree of conversion of monomer to polymer is low.